For example, a known press brake of the electromechanical type is described in the document EP 0 384 529, where a pair of elongated working means cooperate together, and in which one of the two is stationary, while the other one is movable, approaching the first one. The movable working means, in conjunction with the supporting structure, is provided with a plurality of pulleys on which a strap passes, alternately on the pulleys of the supporting structure and on the pulleys of the mobile working means so as to exert an approaching action between the mobile working means and the stationary working means.
As it is known, in the press brake tool machines, supporting structures are provided for, which are designed to be particularly rigid, so as to limit the deformation thereof during the approaching action of the tool to the mould to deform a piece, for example a metallic one, interposed therebetween. The action between the tool and the mould can also reach several hundreds tons, inevitably leading to a deformation of the structure supporting the mould and of the structure handling the tool.
For example, from the document U.S. Pat. No. 6,374,658, it is known to implement a stationary lower panel comprising two slits that are opened on the side edges of the panel, and in which an abutment member is provided for in the proximity of the slot side opening in order to limit the panel deformation.
While being satisfactory under many points of view, however, this solution does not allow, during the press brake action, to compensate for the deformation of the lower panel so as not to sensibly deform the mould secured thereon, especially in the case where the movable upper panel exerts a thrust action, exerted not only laterally, but distributed along the extension of the tool connected thereon.
The document WO 98/46378 shows a structure of a press brake in which the transversal lower beam is stationary, and has a cut centrally that is horizontal and parallel to the mould housing hydraulic jacks, which lift, by deforming it upwardly, the upper part of the transversal lower beam.
While being satisfactory under many points of view, this solution turns out to be particularly complex and expensive to be implemented, forcing to a very elaborate control of the action of the jacks, which action deforms the mould support beam in the opposite direction relative to the stress imposed by the tool. It shall be apparent that the calibration of this device is particularly complex according to the type of processing also on the same piece, to the type of tool and mould that are used, and also as the working piece varies, forcing to continuous and complex maintenance and calibration operations.
A similar solution is shown in the document U.S. Pat. No. 4,640,113.
Another solution is known, for example, from the document U.S. Pat. No. 5,497,647, where the deformation is compensated by using tools that are provided in advance with an imposed deformation, contrary or opposite to the one that will be induced on the machine structure by the processing operations thereof.
Again, this solution, while being satisfactory under some points of view, is particularly complex to be used, forcing to use several machine components, and especially several tools according to the type of the piece and processing operation to be performed.
From what has been stated above, the need is particularly felt, not as much to reduce the deformation caused by the pressure of the tool on the piece, which, in turn, is discharged on the mould deforming the lower panel, but rather the need to control this deformation so that, while accepting the deformation of the lower panel, the dimensional geometric deformation of the mould is limited, allowing to ensure a planarity of the surfaces thereof, which thus maintain the ability to perform processing operations on the piece to be deformed with preset tolerances.
It is also felt the need to manage the press brake movements so as to avoid that the supporting structure is affected by the strong deformations, which from the mobile parts are discharged also on the supporting structure, thus deforming it and altering the measurements of the sensors connected thereupon, which measurements are useful to define the mutual position of the various machine components, such as, for example, the tool position relative to the mould, in fact decreasing the processing tolerances of the press brake machine.
These needs are among other things in sharp contrast with the further needs to have press brakes that are capable of higher and higher actions, and therefore capable to deform the pieces by applying higher and higher forces between the tool and the mould, and applying these forces in ever shorter times in order to reduce the processing cycle times.
The reduction of the processing cycle times forces to increase the handling speeds of the machine components, which increase, accompanied by the increase of the actions, in particular of the forces, between the tool and the mould, increase even more the deformation of the components and the press brake supporting structure, enhancing even more the need for a control of the deformations and the determination of machine management solution that are independent from the strong deformations of the supporting structures.